CMS UE and MB Tunes - University of Floridarfield/cdf/MPI@LHC14_RickField_11-3-14.pdfMPI@LHC 2014 Krakow, November 3, 2014 Rick Field – Florida/CDF/CMS Page 2 CMS UE Tunes ¨PYTHIA

MPI@LHC 2014 Krakow, November 3, 2014

Rick Field – Florida/CDF/CMS Page 1

Outline of Talk

CMS at the LHCCDF “Tevatron Energy Scan”300 GeV, 900 GeV, 1.96 TeV 900 GeV, 7 & 8 TeV

MPI@LHC 2014MPI@LHC 2014Rick Field

University of Florida

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying EventUnderlying Event

Initial-State Radiation

Final-State Radiation

CMS UE and MB Tunes

CMS UE Tunes: Three PYTHA 8 tunes (CTEQ6L, HERALOPDF, NNPDF2.3LO) and one PYTHIA 6 tune (CTEQ6L) from the CMS “Physics Comparisons & Generator Tunes” subgroup.UE Observables: “transMAX”,”transMIN”, “transAVE”, “transDIF”.

Predictions at 13 TeV: Compare the CMS PYTHIA 8 tunes with the Skands Monash tune and the PYTHIA 6 Tune Z2* at 13 TeV.MB Studies: Look at dN/dη and the energy flow in the forward region.

The Energy Dependence of the UE: Detailed look at the energy dependence of the UE and the extrapolation to 13 TeV.



CMS UE TunesCMS UE TunesPYTHIA 6.4 Tune Z2*- CTEQ6L: Start with Tune Z2 and tune to the CMS leading charged particle jet UE data at 900 GeV and 7 TeV. Improved version of Tune Z2.

PTmax Direction Δφ

“Toward”

“TransMAX” “TransMIN”

“Away”

PYTHIA 6.4 Tune CUETP6S1-CTEQ6L: Start with Tune Z2*-lep and tune to the CDF PTmax “transMAX” and “transMIN” UE data at 300 GeV, 900 GeV, and 1.96 TeV and the CMS PTmax “transMAX” and “transMIN” UE data at 7 TeV. Improved version of Tune Z2*.

PYTHIA 8 Tune CUETP8S1-CTEQ6L: Start with Tune 4C and tune to the CDF PTmax “transMAX” and “transMIN” UE data at 900 GeV, and 1.96 TeV and the CMS PTmax “transMAX” and “transMIN” UE data at 7 TeV. Exclude 300 GeV data. Improved version of Tune 4C.

PYTHIA 8 Tune CUETP8S1-HERALOPDF: Start with Tune 4C and tune to the CDF PTmax“transMAX” and “transMIN” UE data at 900 GeV, and 1.96 TeV and the CMS PTmax“transMAX” and “transMIN” UE data at 7 TeV. Exclude 300 GeV data. Improved version of Tune 4C.

PYTHIA 8 Tune CUETP8M1-NNPDF2.3LO: Start with the Skands Monash-NNPDF2.3LO tune and tune to the CDF PTmax “transMAX” and “transMIN” UE data at 900 GeV, and 1.96 TeVand the CMS PTmax “transMAX” and “transMIN” UE data at 7 TeV. Exclude 300 GeV data.



CMS CMS Tune CUETP8S1Tune CUETP8S1--CTEQ6L CTEQ6L

18001800ecmRef

0.210570.19ecmPow

3

0.50

2.0

1.0

0.4

0.4

0.1383

0.137

0.135

0.135

1.5

2.0

2.085

CTEQ6L

4C

3Tune:ee

0.50BeamRemnants:primordialKTsoft

2.0BeamRemnants:primordialKThard

1.0BeamRemnants:halfScaleForKT

0.4TimeShower:pTminChgQ

0.4TimeShower:pTmin

0.1383TimeShower:alphaSvalue

0.137SpaceShower:alphaSvalue

0.135SigmaProcess:alphaSvalue

0.135MultipartonInteractions:alphaSvalue

3.31257reconnectRange

1.60889expPow

2.1006pT0Ref

CTEQ6LPDF

CMS1

PYTHIA 8 Tunes: Corke & Sjöstrand Tune 4C-CTEQ6L and CMS Tune CUETP8S1-CTEQ6L (CMS1).

CMS Tune CUETP8S1-CTEQ6LpT0Ref = 2.1006ecmPow = 0.21057ecmRef = 1800

3.18513

2.7967

2.1391.96

1.8150.9

1.4400.3

pT0 (GeV/c)Ecm (TeV)

pT0(Ecm)=pT0Ref × (Ecm/ecmRef)ecmPow

Start with Tune 4C and vary 4 parameters!



CMS Tune CMS Tune MonashMonashStarStar

70007000ecmRef

0.252080.2150ecmPow

77Tune:ee

0.90.9BeamRemnants:primordialKTsoft

1.81.8BeamRemnants:primordialKThard

1.51.5BeamRemnants:halfScaleForKT

0.50.5TimeShower:pTminChgQ

0.50.5TimeShower:pTmin

0.13650.1365TimeShower:alphaSvalue

0.13650.1365SpaceShower:alphaSvalue

0.130.13SigmaProcess:alphaSvalue

0.130.13MultipartonInteractions:alphaSvalue

1.801.80reconnectRange

1.61.85expPow

2.4023742.280pT0Ref

NNPDF2.3LONNPDF2.3LOPDF

MonashStarMonash

PYTHIA 8 Tunes: Peter Skands Tune Monash-NNPDF2.3LO and CMS Tune CUETP8M1-NNPDF2.3LO (MonashStar).

CMS Tune MonashStarpT0Ref = 2.402374ecmPow = 0.25208ecmRef = 7000

2.80813

2.4027

1.7431.96

1.4320.9

1.0860.3

pT0 (GeV/c)

Ecm(TeV)

Skands-MonashpT0Ref = 2.280ecmPow = 0.2150ecmRef = 7000

2.60513

2.2807

1.7341.96

1.4670.9

1.1580.3

pT0 (GeV/c)

Ecm(TeV)

Start with Monash and change 3 parameters!

from CMS



UE ObservablesUE Observables“Transverse” Charged Particle Density: Number of charged particles (pT > 0.5 GeV/c, |η| < ηcut) in the “transverse” region as defined by the leading charged particle, PTmax, divided by the area in η-φ space, 2ηcut×2π/3, averaged over all events with at least one particle with pT > 0.5 GeV/c, |η| < ηcut.

PTmax Direction

Δφ

“Toward”

“Transverse” “Transverse”

“Away”

“Transverse” Charged PTsum Density: Scalar pT sum of the charged particles (pT > 0.5 GeV/c, |η| < ηcut) in the “transverse”region as defined by the leading charged particle, PTmax, divided by the area in η-φ space, 2ηcut×2π/3, averaged over all events with at least one particle with pT > 0.5 GeV/c, |η| < ηcut. “Transverse” Charged Particle Average PT: Event-by-event <pT> = PTsum/Nchg for charged particles (pT > 0.5 GeV/c, |η| < ηcut) in the “transverse” region as defined by the leading charged particle, PTmax, averaged over all events with at least one particle in the “transverse”region with pT > 0.5 GeV/c, |η| < ηcut.

Zero “Transverse” Charged Particles: If there are no charged particles in the “transverse”region then Nchg and PTsum are zero and one includes these zeros in the average over all events with at least one particle with pT > 0.5 GeV/c, |η| < ηcut. However, if there are no charged particles in the “transverse” region then the event is not used in constructing the “transverse”average pT.

ηcut = 0.8



UE ObservablesUE Observables“transMAX” and “transMIN” Charged Particle Density: Number of charged particles (pT > 0.5 GeV/c, |η| < 0.8) in the the maximum (minimum) of the two “transverse” regions as defined by the leading charged particle, PTmax, divided by the area in η-φ space, 2ηcut×2π/6, averaged over all events with at least one particle with pT> 0.5 GeV/c, |η| < ηcut.

PTmax Direction Δφ

“Toward”


“Away”

“transMAX” and “transMIN” Charged PTsum Density: Scalar pTsum of charged particles (pT > 0.5 GeV/c, |η| < 0.8) in the themaximum (minimum) of the two “transverse” regions as defined by the leading charged particle, PTmax, divided by the area in η-φspace, 2ηcut×2π/6, averaged over all events with at least one particle with pT > 0.5 GeV/c, |η| < ηcut.

Note: The overall “transverse” density is equal to the average of the “transMAX” and “TransMIN”densities. The “TransDIF” Density is the “transMAX” Density minus the “transMIN” Density

“Transverse” Density = “transAVE” Density = (“transMAX” Density + “transMIN” Density)/2

“TransDIF” Density = “transMAX” Density - “transMIN” Density

ηcut = 0.8Overall “Transverse” = “transMAX” + “transMIN”



““transMINtransMIN”” & & ““transDIFtransDIF””The “toward” region contains the leading “jet”, while the “away”region, on the average, contains the “away-side” “jet”. The “transverse” region is perpendicular to the plane of the hard 2-to-2 scattering and is very sensitive to the “underlying event”. For events with large initial or final-state radiation the “transMAX”region defined contains the third jet while both the “transMAX”and “transMIN” regions receive contributions from the MPI and beam-beam remnants. Thus, the “transMIN” region is very sensitive to the multiple parton interactions (MPI) and beam-beam remnants (BBR), while the “transMAX” minus the “transMIN” (i.e.“transDIF”) is very sensitive to initial-state radiation (ISR) and final-state radiation (FSR).

“TransDIF” density more sensitive to ISR & FSR.

PTmax Direction

Δφ


“Toward”

“Away”

“Toward-Side” Jet

“Away-Side” Jet

Jet #3

“TransMIN” density more sensitive to MPI & BBR.

0 ≤ “TransDIF” ≤ 2×”TransAVE”

“TransDIF” = “TransAVE” if “TransMIX” = 3×”TransMIN”



MB&UE Working Group

CMS

ATLAS

MB & UE Common Plots

The LPCC MB&UE Working Group has suggested several MB&UE “Common Plots” the all the LHC groups can produce and compare with each other.

Proton Proton

“Minimum Bias” Collisions

Proton Proton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying EventUnderlying Event

Initial-State Radiation

Final-StateRadiation



UE Common PlotsUE Common Plots

"Transverse" Charged PTsum Density: dPT/dηdφ

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CMS (solid red)ATLAS (solid blue)ALICE (open black)

RDF Preliminary corrected data

"Transverse" Charged Particle Density: dN/dηdφ

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corrected data

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"Transverse" Charged PTsum Density: dPT/dηdφ

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"Transverse" Charged Particle Density: dN/dηdφ

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Charged Particles (|η| < 0.8, PT > 0.5 GeV/c)





CDF versus CMSCDF versus CMS

CDF and LHC data at 900 GeV/c on the charged particle density in the “transverse”region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.

CDF and LHC data at 900 GeV/c on the charged PTsum density in the “transverse”region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are corrected to the particle level with errors that include both the statistical error and the systematic uncertainty.

"TransAVE" Charged Particle Density: dN/dηdφ

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"TransAVE" Charged PTsum Density: dPT/dηdφ

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CMS

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CDF versus LHCCDF versus LHC



CUETP8S1CUETP8S1--CTEQ6LCTEQ6L

CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are compared with PYTHIA 8 Tune CUETP8S1-CTEQ6L (excludes 300 GeVin fit).

"TransAVE" Charged Particle Density

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CMS Tune CUETP8S1-CTEQ6L


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CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are compared with PYTHIA 6.4 Tune Z2*.


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7 TeVTune Z2*-CTEQ6L



CUETP8S1CUETP8S1--CTEQ6LCTEQ6L"TransAVE" Charged PTsum Density

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CMS Tune CUETP8S1-CTEQ6L


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"TransAVE" Charged PTsum Density

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7 TeVTune Z2*-CTEQ6L


CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged PTsumdensity in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are compared with PYTHIA 6.4 Tune Z2*.

CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged PTsumdensity in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are compared with PYTHIA 8 Tune CUETP8S1-CTEQ6L (excludes 300 GeVin fit).



CUETP8M1CUETP8M1--NNPDF2.3LONNPDF2.3LO

CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are compared with the PYTHIA 8 Tune Monash-NNPDF2.3LO.

CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are compared with the PYTHIA 8 Tune CUETP8M1-NNPDF2.3LO (excludes 300 GeV in fit).


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7 TeVCUETP8M1-NNPDF2.3LO


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7 TeVMonash-NNPDF2.3LO



Energy DependenceEnergy Dependence

CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged PTsumdensity in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are compared with the PYTHIA 8 Tune Monash-NNPDF2.3LO.

CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged PTsumdensity in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are compared with the PYTHIA 8 Tune CUETP8M1-NNPDF2.3LO (excludes 300 GeV in fit).


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7 TeVMonash-NNPDF2.3LO


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7 TeVCUETP8M1-NNPDF2.3LO




CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8.

CMS and CDF data on the charged particle density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8 with 5 < PTmax < 6 GeV/c. The data are plotted versus the center-of-mass energy (log scale).


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CMS solid dotsCDF solid squares

13 TeV



Energy DependenceEnergy Dependence"TransAVE" Charged Particle Density: dN/dηdφ

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Energy DependenceEnergy Dependence"TransAVE" Charged Particle Density: dN/dηdφ

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Tune Z2*-CTEQ6L (green line)CUETP8S1-CTEQ6L (black line)Monash-NNPDF2.3LO (red line)

CUETP8M1-NNPDF2.3LO (blue line) 13 TeV




CMS and CDF data on the charged particle density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8 with 5 < PTmax < 6 GeV/c. The data are plotted versus the center-of-mass energy (log scale). The data are compared with PYTHIA 6 Tune Z2* and PYTHIA 8 Tune CUETP8S1, Tune Monash, and Tune CUETP8M1.


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CUETP8M1-NNPDF2.3LO (blue line)


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CMS and CDF data on the charged PTsumdensity in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8 with 5 < PTmax < 6 GeV/c. The data are plotted versus the center-of-mass energy (log scale). The data are compared with PYTHIA 6 Tune Z2* and PYTHIA 8 Tune CUETP8S1, Tune Monash, and Tune CUETP8M1.

13 TeV13 TeV



Predictions at 13 Predictions at 13 TeVTeV"TransMAX" Charged Particle Density

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"TransMIN" Charged Particle Density

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"TransMAX" Charged PTsum Density

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Predictions at 13 Predictions at 13 TeVTeV"TransAVE" Charged Particle Density

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"TransDIF" Charged Particle Density

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Predictions at 13 Predictions at 13 TeVTeV

CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged particle density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are compared with PYTHIA 6 Tune Z2* and PYTHIA 8 Tune CUETP8S1, Tune Monash, and Tune CUETP8M1.

CMS and CDF data on the charged particle density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8 with 5 < PTmax < 6 GeV/c. The data are plotted versus the center-of-mass energy (log scale). The data are compared with PYTHIA 6 Tune Z2* and PYTHIA 8 Tune CUETP8S1, Tune Monash, and Tune CUETP8M1.


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CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged PTsum density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are compared with PYTHIA 6 Tune Z2* and PYTHIA 8 Tune CUETP8S1, Tune Monash, and Tune CUETP8M1.



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CMS data at 7 TeV and CDF data at 1.96 TeV, 900 GeV, and 300 GeV on the charged PTsum density in the “transAVE” region as defined by the leading charged particle (PTmax) for charged particles with pT > 0.5 GeV/c and |η| < 0.8. The data are compared with PYTHIA 6 Tune Z2* and PYTHIA 8 Tune CUETP8S1, Tune Monash, and Tune CUETP8M1.



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I believe we knowwhat the UE will look

like at 13 TeV!



Charged Particle DensityCharged Particle Density

The charged particle density, dN/dη, for charged particles with pT > 40 MeV/c at 7 TeV predicted by the Monash tune for the non-diffractive component (ND) and the inelastic component (IN = ND+SD+DD).

The ratio on the inelastic component (IN = ND+SD+DD) and the non-diffractive component (ND) for the charged particle density, dN/dη, for charged particles with pT > 40 MeV/c as predicted by the Monash tune at 7 TeV.

Charged Particle Density: dN/dη

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IN = ND + SD + DD

ND


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(ND+SD+DD)/ND




The charged particle density, dN/dη, for charged particles with pT > 40 MeV/c at 7 TeV predicted by the Monash tune for the non-diffractive component (ND) and the inelastic component (IN = ND+SD+DD).

The ratio on the inelastic component (IN = ND+SD+DD) and the non-diffractive component (ND) for the charged particle density, dN/dη, for charged particles with pT > 40 MeV/c as predicted by the Monash tune at 7 TeV.


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(ND+SD+DD)/NDAdding SD+DD reduces the ND contribution by ≈ 22%!




The charged particle density, dN/dη, for charged particles with pT > 40 MeV/c at 7 TeVpredicted by the Monash tune and the CMS tune CMS tune CUETP8S1-CTEQ6L for the inelastic component (IN = ND+SD+DD).

The charged particle difference, ΔNchg, for charged particles with pT > 40 MeV/c at 7 TeVbetween the Monash tune and the CMS tune CMS tune CUETP8S1-CTEQ6L for the inelastic component (IN = ND+SD+DD), where ΔNchg = Nchg(Monash)-Nchg(CMS1) and corresponds to the number of charged particles in 0.5 η.


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Nchg Difference: Nchg(Monash)-Nchg(tune)

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The charged particle density, dN/dη, for charged particles with pT > 40 MeV/c at 7 TeVpredicted by the Monash-NNPDF2.3LO tune, the tune CUETP8S1-CTEQ6L (CMS1), and tune CUEP8M1-NNPDF2.3LO (Mstar) for the inelastic component (IN = ND+SD+DD).

Shows the charged particle difference, ΔNchg, for charged particles with pT > 40 MeV/c at 7 TeV between the Monash-NNPDF2.3LO tune and tune CUETP8S1-CTEQ6L (CMS1), and tune CUEP8M1-NNPDF2.3LO (Mstar) for the inelastic component (IN = ND+SD+DD), where ΔNchg = Nchg(Monash)-Nchg(tune) and corresponds to the number of charged particles in 0.5 η.


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Nchg Difference: Nchg(Monash)-Nchg(tune)

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Energy Flow: Energy Flow: dEdE/d/dηη

The energy density, dE/dη, at 7 TeV predicted by the Monash tune for the non-diffractive component (ND) and the inelastic component (IN = ND+SD+DD).

The ratio on the inelastic component (IN = ND+SD+DD) and the non-diffractive component (ND) energy density, dE/dη, predicted by the Monash tune at 7 TeV.

Energy Density: dE/dη

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The energy density, dE/dη, at 7 TeV predicted by the Monash tune for the non-diffractive component (ND) and the inelastic component (IN = ND+SD+DD).

The ratio on the inelastic component (IN = ND+SD+DD) and the non-diffractive component (ND) energy density, dE/dη, predicted by the Monash tune at 7 TeV.


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(ND+SD+DD)/NDAdding SD+DD reduces the ND contribution by ≈ 23%!



Energy Flow: Energy Flow: dEdE/d/dηηEnergy Density: dE/dη

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Energy Difference: E(Monash)-E(tune)

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ForwardRegion

The energy density, dE/dη, at 7 TeV predicted by the Monash-NNPDF2.3LO tune and the tune CUETP8S1-CTEQ6L (CMS1) for the inelastic component (IN = ND+SD+DD).

The energy difference, ΔE, at 7 TeV between the Monash-NNPDF2.3LO and tune CUETP8S1-CTEQ6L (CMS1) for the inelastic component (IN = ND+SD+DD), where ΔE = E(Monash)-E(CMS1) and corresponds to the amount of energy in GeV in 0.5 η.




Shows the energy density difference, ΔE, at 7 TeV between the Monash-NNPDF2.3LO tune, and tune CUETP8S1-CTEQ6L (CMS1), and tune CUEP8M1-NNPDF2.3LO (Mstar) for the inelastic component (IN = ND+SD+DD), where ΔE = E(Monash)-E(tune) and corresponds to the amount of energy in GeV in 0.5 η.

Energy Difference: E(Monash)-E(tune)

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Tuning the PDF!Tuning the PDF!

x0

slope

Start with the HERALOPDF functions, f(x). Modify the gluon distribution at small x by adding a function f1(x,p1,p2) with 2 parameters (p1 = x0, p2 = slope).

x0

New ApproachTune the PDF

Started with the SkandsMonash-NNPDF2.3LO tune!



TOTEM Forward TOTEM Forward dNdN/d/dηη

Use the CMS Tune CUETP8S1-HERALOPDF and vary the low x gluon distribution to try to improve the fit to the forward region (TOTEM data). Need to increase the gluon distribution at x < ≈ 10-5!



TOTEM Forward TOTEM Forward dNdN/d/dηηCan improve agreement

with TOTEM!

MPI contributes a lot to both central and forward dN/dη!



TOTEM Forward TOTEM Forward dNdN/d/dηη

Use the CMS Tune CUETP8S1-HERALOPDF and vary the low x gluon distribution to try to improve the fit to the forward region (TOTEM data).

Can improve agreement with TOTEM! Does not affect the central region.

However, changing thegluon distribution at low x

destroys the fit to the UE data!If you change the PDF, youmust change the UE tune

accordingly!



ReRe--Tune the UE ParametersTune the UE Parameters

Starting with the tunes that fit to the forward region (TOTEM data) re-tune the UE parameters of CMS Tune CUETP8S1-HERALOPDF to fit the UE data.

Need to start with a slightly different low x gluon distribution or do a simultaneous fit that varies both the low x gluon distribution and the UE parameters in an attempt to fit the central and forward dN/dη and the UE data.

Oops! Now agrees in the central region and is low

in the forward region.



Try AgainTry Again

Starting with a different low x gluon distribution re-tune the UE parameters of CMS Tune CUETP8S1-HERALOPDF to fit the UE data.

Perhaps we should do a simultaneous fit that varies both the low x gluon distribution and the UE parameters in an attempt to fit the central and forward dN/dη and the UE data.

Not bad! Now fits the forward region and the UE data. A little low in

the central region.

Before UE tuning After UE tuning



Try AgainTry Again

Starting with a different low x gluon distribution re-tune the UE parameters of CMS Tune CUETP8S1-HERALOPDF to fit the UE data.

Perhaps we should do a simultaneous fit that varies both the low x gluon distribution and the UE parameters in an attempt to fit the central and forward dN/dη and the UE data.

Not bad! Now fits the forward region and the UE data. A little low in

the central region.

Before UE tuning After UE tuning

Stay tuned! More CMS tunes coming!

Documents

CMS UE and MB Tunes - University of Floridarfield/cdf/MPI@LHC14_RickField_11-3-14.pdfMPI@LHC 2014 Krakow, November 3, 2014 Rick Field – Florida/CDF/CMS Page 2 CMS UE Tunes ¨PYTHIA